The present invention relates to a circuit breaker with a self-illuminating power switch which can be used as a power switch for electrical equipment or electronic circuits and devices.
The applicant of this application has previously proposed a circuit breaker and a combined circuit breaker and switch structure in Japanese Utility Model Applications Laid Open Nos. 63-202037 and 2-50931.
The combined circuit breaker and switch functions simultaneously as a circuit breaker and as a power switch, and in the case where it is employed as a power switch of a device, the circuit breaker is automatically actuated to protect the device when an overcurrent flows due to a failure of the device.
With such an integrated structure, the switch and the circuit breaker are installed at one time, not separately, and the space occupied by them decreases--this attains miniaturization of the device.
FIG. 1 shows the construction of the above-mentioned combined circuit breaker and switch. Reference numeral 11 indicates a case made of an insulating material. The case 11 has its underside closed with a bottom panel 12, and a circuit breaker 20 and a switch 30 are housed in a space defined by the case 11 and the bottom panel 12.
The circuit breaker 20 comprises: a first terminal 21 planted on the bottom panel 12 in the case 11 at one corner thereof; a thermal plate 22 as of bimetal extending along the inner wall surface 11A of the case 11 but fixed at one end to the first terminal 21; a plate-like movable piece 23 coupled at one end to the free end 22A of the thermal plate 22 and extending toward the first terminal 21; a first movable contact 24 provided on the movable piece 23 near its free end; a bow-shaped spring 25 held between the free end of the movable piece 23 and the inner wall of the case 11 (the inner wall of an edge flange 13 raised from the bottom panel 12 in this example), for applying compressive force to the movable contact piece 23 lengthwise thereof; and a first fixed contact 26 provided opposite the first movable contact 24.
The switch 30 comprises; a fulcrum plate 31 fixedly mounted on the bottom panel 12; a plate-like pivotal piece 32 supported by the fulcrum plate 31 for seesawing; a second movable pivotal 33 provided on the contact piece 32 at one free end thereof; a second fixed contact 34 which is engaged with and disengaged from the second movable contact 33; a second terminal 35 for leading the second fixed contact 34 out of the case 11; a switching actuator 36 supported on the top of the case 11 so that it can seesaw about a pin 36S; and an actuating lever 37 extending from the switching actuator 36 toward the pivotal piece 32 to elastically press it. The actuating lever 37 is shown to be composed of a sleeve 37A extending from the underside of the switching actuator 36, a spring 37B housed in the sleeve 37A, and a push rod 37C which is slidably received in the sleeve 37A and is elastically pressed out therefrom by the force of the spring 37B to abut against the top surface of the pivotal piece 32.
Reference numeral 38 indicates reset means for resetting the circuit breaker 20. In this example the reset means is formed by a projecting piece 38A extending down from one free end of the switching act 36 and having a tapered edge 38B. The tapered edge 38B of reset means 38 presses the coupling portion of the thermal plate 22 and the movable contact 23 toward the inner wall 11A of the case 11 so that the circuit breaker 20 in its open state is reset to its closed state.
In this combined circuit breaker and switch, the first movable contact 24 and the first fixed contact 26 forming the breaker 20 are normally held in contact with each other by the biasing force of the bow-shaped spring 25. By actuating the switching actuator 36 in this state, the push rod 37C reciprocates on the top surface of the pivotal piece 32 lengthwise thereof, passing through its center of rotational movement, by which the pivotal piece 32 performs a stable seesaw motion with the fulcrum plate 31 as the supporting point. As a result, the second movable contact 33 and the second fixed contact 34 are brought into and out of electrical contact with each other; hence, the path between the first and second terminals 21 and 35 are switched between conducting and nonconducting states, serving as a switch.
Incidentally, a U-shaped spring piece 39 is interposed between the pivotal piece 32 and the fulcrum plate 31, by which even if the former jumps up from the latter when the switch 30 makes, their mechanical coupling is retained, thus preventing the generation of chattering between them.
When the switch 30 is actuated to be conducting, current flows between the first and second terminals 21 and 35 via the route through thermal plate 22, movable piece 23, first movable contact 24, first fixed pivotal 26, fulcrum plate 31, contact piece 32, second movable contact 33, second fixed contact 34, and second terminal 35, sequentially, in this order.
When the current exceeds a predetermined value, the thermal plate 22 generates heat by the Joule's heat and starts bending with the heat. In the illustrated example the thermal plate 22 is deformed so that its free end 22A shifts toward a stopper 14 protrusively provided on the bottom panel 12.
As the free end 22A of the thermal plate 22 moves toward the stopper 14, the movable piece 23 will be forced to turn about the first fixed contact 26. As a result of this, the point of engagement between the movable piece 23 and the bow-shaped spring 25 shifts toward the outside of a line joining the point of contact between the first movable contact 24 and the first fixed contact 26 and the point of engagement between the bow-shaped spring 25 and the edge flange 13 (that is, toward the inner wall 11A of the case 11).
Once the point of engagement between the movable piece 23 and the bow-shaped spring 25 goes beyond the line joining the point of contact between the first movable contact 24 and the first fixed contact 26 and the point of engagement between the spring 25 and the edge flange 13, the direction of the lateral biasing force of the spring 25, that is, the direction of force by which the first movable contact 24 is urged against the first fixed contact 26, is reversed and the point of engagement between the movable piece 23 and the spring 25 leaps toward the inner wall 11A of the case 11, disengaging the first movable contact 24 from the first fixed contact 26 to provide nonconduction between the first and second terminals 21 and 35.
At this time, the free end portion of the movable piece 23 coupled with the free end 22A of the thermal plate 22 engages the stopper 14, and by its reaction force, the point of engagement between the spring 25 and the movable piece 23 remains greatly biased toward the inner wall 11A of the case 11. This state is retained even after the temperature of the thermal plate 22 drops down to its initial temperature.
When actuating the switching actuator 36 to turn off the switch 30 after the temperature of the thermal plate 22 has returned to the initial temperature, the tapered edge 38B of the projecting piece 38A forming the reset means 38 engaged coupled the free ends of the thermal plate 22 and the movable piece 23 and pushes them toward the inner wall 11A of the case 11. When the free end of the movable piece 23 is moved out of the line joining the point of engagement between the movable piece 23 and the spring 25 and the point of engagement between the spring 25 and the edge flange 13 of the case 11, the lateral biasing force of the spring 25 is reversed in direction, bringing the first movable contact 24 into contact with the first fixed contact 26 and hence resetting the switch 30.
In the circuit breaker 20 the top end of the first terminal 21 is extended upward to form a projecting piece 27, which is received in a hole 15 made in the top panel of the case 11. The breaking characteristic (quick-break, slow-break) of the circuit breaker 20 is controlled through adjustment of the direction of the thermal plate 22 by turning the projecting piece 27 with a jig.
With the combined circuit breaker and switch unit described above, a pilot lamp for indicating power supply must be provided separately of the unit. This requires a site for attachment of the pilot lamp and involves work for its installation.
Besides, when the combined circuit breaker and switch unit is used as a power switch at a dark place, it is necessary to provide a light source for illuminating the position of the switching actuator of the switch.